Constant tension letoff mechanism



June 6, 1944. c D. BROWN CONSTANT TENSION LET-OFF MECHANISM Filed Nov. 30, 1942 INVENTOR. CARL D. BROWN M ?K ATTORNEY Patented June 6, 1944 CONSTANT TENSION LETOFF MECHANISM Carl D. Brown, llopedale, Mass, assignor to Draper Corporation, Hopedale, Mass., at corporation of Maine Application November 30, 1942, Serial No. 467,331

8 Claims.

The present invention relates generally to improvements in let-off mechanisms forlooms and,

as. illustrated herein, relates more particularly- Let-offs of the positive type usually comprise a 4 warp beam geared to a transmitting shaft which is driven by suitable mechanism connected to the loom. The transmitting shaft is intermittently rotated and transmits th required rotary movement to the warp beam. The rate of let-oil is controlled by mechanism which is responsive to the decrease in diameter of the Warp on the warp beam. In order to form cloth of increased quality, the warp sheet must be maintained under an even and uniform tension and I have found that, by oscillating the warp beam during operation of the loom, such a result is easily attained.

One object of the present invention, accordingly, is to provide a loom with a positive type of let-off whereby the warp i maintained under an even and uniform tension. To this end, the letoff mechanism is provided with a warp beam which is rotatable to let-off Warp. means for D itively rotating the warp beam in one direction to let-oil warp, and means controlled by the tension of the warp for rotating the warp beam in the opposite direction to take up warp and thus compensate for any variations in warp tension. As illustrated, the warp is maintained under a predetermined and uniform tension by a weight, which is effective through the let-oil mechanism to rotate the warp beam to take up warp to compensate for any variation in warp tension.

With the above and other objects in view, the invention will now be described with particular reference to the accompanying drawing which illustrates a preferred embodiment of the invention and in which:

Fig. 1 is a view in side elevation of a portion of the left hand rear side of a loom;

Fig. 2 is a sectional view taken along line II=II of Fig. l; and

Fig. 3 is a view in section taken III-111 of Fig. 1.

.The' illustrated embodiment of the present invention is shown herein as applied to a 100m of usual construction. Only apart of the loom with the improved let-off mechanism attached there'- to is shown in the drawing, the parts of the loom not shown forming no part of the present invention.

The present invention is adapted to be used along the line with any of the so-called "positive" types of letoff. These let-offs include a warp beam geared to a transmitting shaft which is driven from suitable mechanism connectedto the loom.

For the purposes of illustration the preferred embodiment of the invention is shown as incorporating in combination with certain new parts as hereinafter described, certain other parts of a well known type of let-off. The drawing shows a portion of the rear left hand side of a loom and includes a warp beam l0 rotatably mounted in a bearing 12 fixed to the left hand side frame is of the loom. A similar bearing (not shown) is, of course, provided on the right hand side frame.

The let-off comprises a vertical worm shaft I8 rotatably mounted in spaced bearings I8, 20, and 22 formed in a bracket 24 which is pivotally mounted on the side frame i 4 as will later be described. A ratchet wheel 26 is fixed to the lower end of the shaft l6 and a hand wheel 28 is fixed adjacent to the upper end thereof. The shaft I also has fixed thereto intermediate its I ends, a worm 30.

The worm 30 meshes with a worm wheel 32 fixed to a horizontal shaft 34 which is rotatably mounted at one end in a bearing 36 formed in a forward extension 38 of the bracket 24 and adjacent its other end is supported in a bearing 40 fixed to the side frame i4 of the loom. The shaft 34 at its inner end carries a pinion 42 which-meshes with teeth formed in agear 44 fixed to the warp beam it.

A pawl carrier 46 is loosely mounted on the worm shaft is and has pawls 48 and 50 mounted thereon. A rod 52 is pivotally connected to the pawl carrier 46 and is arranged to be pulled forwardly by a reciprocating link 54 to rotate the ratchet wheel 26 and the worm 30 in a direction tion, upon the return of the link 54, by a com-.

to let-off the warp sheet from the warp beam Ill. The rod 52 is returned to its original posipression spring 56.

Mechanism is provided for determining the length of the forward stroke of therod 52 which shaft 60 adjacent to one end thereof and theshaft intermediate its ends and outside of the loom side frame l4 has fixed thereto an upwardly extending arm 02 pivotally connected to the lowe1- end of a substantially vertical link 04. The upper end of the link 54 is pivotally secured to a substantially horizontal armor a bell crank lever pivoted at 88 to the loom irame II. A lever is pivoted at 12 to the loom frame. The lower end of the lever 10 embraces the rod 52 and normally engages a collar 14 fixedly secured to the rod 52.

A rod 16 is pivotally secured at on end to the top of the lever ll and is.pivotally connected at its other end to an arm 18 which is fixed to a shaft 80 mounted in a bearing 82 on a bracket 04 fixed to the side frame of the loom. A similar bracket and bearing (not shown) support the other end of the shaft 00. A whip roll 88 is mounted in a bearing 88 formed in an arm 80 fixed to the shaft 80. A compression spring 82 is mounted on the rod 16 and bears at one end against a depending arm 94 of the bell crank 66 and its other end bears against an adjusting collar 86 fixed to the rod 16. Thus, the position of the-lever 10 is controlled by the diameter of the warp on the warp beam i0 and by the tension oi th warp. The lower-end of the lever 10 engages the collar 14 and thus determines the lost motion between. the link 54 and the rod 52. As the diameter of the warp on the warp beam decreases or the tension on the warp increases the lost motion between the rod 52 and the link 54 also decreases thus providing for greater rotation of the ratchet wheel 26 to eifect greater rotation of the warp beam l0 as the diameter of the warp thereon decreases or the tension on thewarp increases.

As stated above, the bracket 24 is pivotally mounted for rotation about the horizontal shaft 34. Thus any tension on th warp, through the driving connections will tend to rotate the bracket 24 and the vertical worm shaft l6 and the worm 30 carried thereby in a counterclockwise direction. In order to prevent excessive rotation of th bracket 24 and also to control the tension on the warp, the bracket 24 is normally maintained in the position shown in Fig.1 by a weight 98 slidably mounted on a horizontal arm I00 rigidly secured to and extending forwardly from the bracket 24. In order to maintain an even and uniform tension on the warp as its diameter on the warp beam l0 decreases, the position of the weight 88 is controlled by the lever 58. As shown inFig. 1, the warp beam in is nearly empty and the top end of the lever 58 is in its extreme rearward position. The shaft 80, to which the lever 50 i fixed ha a gear segment I02 fixed adjacent to its outer end. The gear segment l02 rotates toward the left as the diameter of the warp on the beam l0 decreases. The weight 88 is provided with teeth I04 which mesh with the teeth on the gear segment I02. Thus as the lever 58 moves inwardly toward the position shown in Fig. l, the weight 88 also moves in the same .direction toward the supporting pivot 34 on which the arm I00 and thebracket 24 are pivotally mounted.

The weight 98is provided with a ledge I06 (Fi 2) which is arranged to engage a shelf I08 formed on the gear segment I02 to prevent the teeth I04 on the weight 98 from damaging the teeth on the gear segment when'the weight is rotated in a counter-clockwise direction during operation of the loom.

During operation of the loom, the rod 52 is moved toward the right by the link 54 and the ratchet wheel 26 and the worm shaft it are rotated 'in a direction to let-oil the warp. The extent of rotation of the ratchet wheel is controlled by the mechanism described above. As the lo'om operates and the tension onthe warp increases or decreases due in part to the op ing and closing or the shed, the bracket 24 and the weight 80 are rotated in clockwise and counterclockwise directions to compensate for the increased or decreased tension on the warp. As the shed closes and the tension onthe warp sheet decreases, the bracket 24 and the weight 00 carried thereby will rotate in a clockwise direction and the warp beam II will be rotated in a direction to take up the slack and thus maintains the warp sheet under uniform tension.

The oscillation of the bracket 24 i permitted I substantially independently of the pawl carrier 48. When the bracket 24 is rotated in a clockwise direction to take-up and thus compensate for any looseness in the warp, the pawl carrier '46 will rotate in a clockwise direction as viewed in Fig. 3, the rod 52 remaining stationary. This clockwise movement of the pawl carrier will rotate the worm 30 and thus require that weight 98 rotate the bracket 24 very slightly farther than would be required if the Worm 30 were not' thus rotated. However, since rotation of the weight 98 and bracket 24 will rotate the shaft 34 through the same angle, and independent rotation of worm 30 by the pawl carrier 48 serves only to feed the worm and bracket s1ightly around the gear 32, the effect of this independent rotation of the worm is comparatively insignificant. When the bracket 24 is rotated in a counter-clockwise direction, the pawl carrier 46 rotates in a counter-clockwis direction and the pawls 48, 50 ride over the teeth on the ratchet wheel 25 without affecting the latter. Ac

- cordingly, the pawl carrier 45 and the pawls 40,

' Patent of the United States is:

1. In a loom let-oil, a warp beam rotatable to let-oil warp, means for positively rotating the warp beam intermittently in one direction tov let-off warp, means controlled by the diameter of the warp on the warp beam for varying the extent of each rotative let-oil movement of the warp beam, and means controlled by said second mentioned means and by the tension of the warp for rotating the warp beam in the other direction to maintain the warp under even and uniform tension.

2. In a loom let-off, a warp beam rotatable to let-off warp, means for positively rotating the warp beam step-by-step in one direction to letoff warp, means responsiv to decrease in diameter of the warp on the warp beam to increase the'extent of rotation of the warp beam, and means controlled by the second mentioned means and by the tension of the warp for rotating the warp beam in'the other direction to take-up slack in the warp produced during operation of the loom.

3. In a let-off for looms, a rotatable warp beam, a horizontal shaft geared to the warp beam, mechanical means actuated by a moving part of the loom for positively rotating said shaft in a direction to efiect let-oil of the warp beam,

shaft in the opposite direction to take up the wa p to maintain the warp under an even and uniform tension during operation of the loom.

4. In a letoii' for looms, a rotatable warp beam, a horizontal shaft geared to the warp beam, a support pivoted on said shaft, mechanical means mounted on said support for imparting a step by step rotary motion to the shaft to let oiI warp, automatic means for controlling the extent of tep-by-step movement, means connected to said support and acting upon said shaft to rotate said shaft in the opposite direction to takeup warp and connections between said last named means and said automatic means for controlling rotation of the shaft to take up warp to maintain the warp under even and uniform tension during operation of the loom.

5. In a let-oil. for looms, a rotatable warp beam, a horizontal shaft geared to the warp beam, a support pivoted on said shaft, mechanical means mountedon said support for imparting a steP-by-stcp' rotary motion to the shaft to let off warp. automatic means for controlling the extent of step-by-step movement, a weight slidably mounted on said support and effective to rotate said support and said shaft in the opposite direction to take up the warp, and connections between said weight and said-automatic means for controlling the position of said weight on said bracket for maintaining the warp under uniform tension during operation of the loom.

6. In a let-off for looms, a rotatable warp beam, 9. horizontal jshaft geared to the warp beam, a support pivoted on said shaft, mechanical means mounted on said support for imparting a step-by-step rotary motion to the shaft to let-oi! warp, automatic means. for controlling the extent of step-by-step movement, a substantially horizontally extending arm fixed to said support, a weight slidably moimted on said am arranged to rotate said upport and said shaft in the opposite direction to effect take-up of the warp on the warp beam, and connections between said weight and said automatic means for sliding the weight along said arm to vary the moment of said weight directly in accordance with the varying diameter ofthe warp on the warp beam to maintain the warp under uniform tension during the operation of the loom.

shaft mounted in said bracket, a ratchet wheel fixed to one end of said vertical shaft, a worm fixed to said vertical shaft intermediate its ends, a worm wheel fixed on said horizontal shaft and meshing with said worm, a pawl carrier mounted on said vertical shaft and having a pair of pawls thereon for engaging teeth on said ratchet wheel, means for rotating said .pawl carrier in a direction to rotate said ratchet wheel, automatic means controlled by the diameter of the warp on the warp'beam for determining the extent of rotation of said pawl. carrier, a substantially horizontal arm fixed to said bracket, a weight slidably mounted on said arm,-and means on said automatic means engaging said w ight a d p sitloning said weight on said arm in accordance 8. In a let-off for looms, a rotatable warp I beam, a horizontal shaft geared to the warp beam, a bracket pivoted on said shaft, a vertical shaft mounted in said bracket, a ratchet wheel fixed to one end of said vertical shaft, a worm fixed to said vertical shaft intermediate its ends, a worm wheel fixed on said horizontal shaft and meshing with said worm, a pawl carrier mounted on said vertical shaft and having a pair of pawls thereon for engaging teeth on said ratchet wheel, means for rotating said pawl carrier in a'direction to rotate said ratchet wheel, automatic means controlled by the diameter of the warp on the warp beam' for determining the extent of rotation of said pawl carrier, a substantially horizontal arm fixed to said bracket, a weight slidably mounted on said arm, said weight being effective to rotate said horizontal shaft in the opposite di- 

